Heretofore, motors which use a small-sized, thin and short-cylindrical or flat winding and permanent magnets for producing a magnetic field generally have had the magnets installed within the winding. In a brushless motor, permanent magnets are included in a fixed winding and caused to rotate. The brushless motor is essentially the same in relative arrangement as coreless motors and slotless motors where a winding is rotated. Accordingly, a motor in which magnets for developing a magnetic field are fixed is hereinafter described.
In a motor having a winding in the form of a short cylinder, magnetic flux produced in the gaps between the magnets lies chiefly radially, but it does not exist on the end surfaces on which the magnets are installed. In the open end surfaces opposite to these end surfaces, leakage flux that accounts for about 10 to 20% is developed axially. In a motor having a flat winding, magnetic flux is set up mainly axially, and leakage flux that accounts for about 10 to 20% of the magnetic flux is generated radially. In the prior art, these leakage fluxes have not been positively employed. For instance, the winding disclosed in U.S. Pat. No. 3,191,081 is a hollow cylinder, and therefore it can in no way make use of the axial leakage flux. The winding shown in U.S. Pat. No. 2,513,410 takes the form of a cylinder having shoulder and bottom portions. In the peripheral regions close to the axis, stringlike wire elements overlap one another, so that the axial air gaps become too large. Also, it is not expected that the leakage flux is employed by taking the axial component corresponding to the field poles. Further, the winding disclosed in Japanese Patent Publication No. 952/1964 is not able to make use of the radial leakage flux, because it is a flat disk adopting an involute. In addition, the winding in the form of printed coils disclosed in Japanese Patent Laid-Open Application No. 78104/1974 is not capable of utilizing the radial leakage flux, because it is a flat disk bordered with inner and outer ribs.